You will need a pair of pliers to GENTLY remove the 30274 ejector arm from the Gen4 housing that you ordered. Once it is out, put it in your Gen3 housing. Also make sure you install the HRED backwards from the stock plunger configuration.
No need for an APEX extractor.

There are dozens of people who I know of that did NOT have that combination fix the ejection issue for them. I only tested the HRED as I was sent the incorrect LWD extractor. There is a lot of engineering and testing behind Apex's extractor and I'm proud to be a small piece of it and for it to fix almost every problem gun out there by dropping it in. Others needed fitting.